Wager . — The Nucleus of the Yeast-Plant. 51 1 
following manner, by which permanent preparations can be 
made. The cover-glass preparation is stained for two hours, 
washed in water, then in 70 °/ 0 alcohol, then again in water 
and in 70 °/ o alcohol, and so on until on examination under 
the microscope the protoplasm appears clear. It is then 
washed quickly in methylated alcohol and absolute alcohol, 
cleared in xylol and mounted in Canada-balsam. The 
nuclear body is coloured red and perfectly differentiated from 
the colourless protoplasm. 
Methyl-green and eosin. By this combination the vacuole 
and its contents are stained green or blue, the protoplasm 
and nuclear body pink. The stain is allowed to act for one-half 
to two minutes ; the preparation is then washed in water and 
examined in dilute glycerin. Permanent preparations may 
be made by drying up completely after washing in water, 
then clearing in xylol and mounting in balsam. 
The successful application of these two methods depends 
to a large extent upon the judgment of the investigator in 
determining the right moment at which to stop the washing 
out in water or alcohol. 
Haematoxylin. A dilute solution of Delafield’s haemato- 
xylin in water, allowed to act on Yeast-cells for several hours, 
which are then washed in water and 2 °/ Q alum solution, 
generally shows up the nuclear body quite clearly. The 
preparation may be washed in alcohol, cleared in xylol, and 
mounted in balsam. Good preparation can also be obtained 
by Heidenhains iron-alum method. The cover-glass prepara- 
tions are first of all mordanted in a 2*5 °/ 0 solution of iron- 
alum in water for about three hours. They are then well 
washed in water and stained in a *5 °/ 0 solution of haemato- 
xylin in distilled water for six to twelve hours, then they 
should be washed well in water, and soaked again in the 
iron-alum solution. In this the stained portions turn black, 
but are then gradually decolourized by a prolonged stay in 
the solution. After about two or three days, or sometimes 
more, the stain is found to have nearly disappeared from all 
parts of the cell except the nuclear body, but sometimes 
